Table of Contents

CC2500

The CC2500 module is necessary to support the Skyartec and Frsky protocols. It is possible to scavenge this module from a Skyartec transmitter or to purchase it standalone. When searching ebay or aliexpress, searching for ‘CC2500 PA’ will often return reasonable results
The small CC2500 is very small - about 17×12 mm. It has no PA and no LNA, It supports some telemetry, as I get voltage but no RSSI. A quick range test showed no problems out to over 100 meters using a FrSky D4R-II, at which point I ran out of room.

Frequency tuning

The CC2500 allows software to tune the frequency. This should be available for all the CC2500 protocols on the protocol settings page as the Fine and Coarse settings. The proper settings for this depend on the protocol and RF module in your transmitter, so needs to be set for each model.

As of this writing, the Fine adjustment has been sufficient for the combinations we've seen. It ranges from -128 to +127, defaulting to 0. Try adjusting it by steps of 10 to 20 until the model binds. Once it's bound, keep stepping the value until the connections fails. Then set it to half-way between those two values.